Muscles of the Back, Neck, Thorax, and Abdomen: Key Structures and Functions

Splenius Capitis origin

Nuchal ligament and spinous processes of C7-T3 or T4.

Splenius Capitis insertion

Mastoid process of the temporal bone and lateral third of the superior nuchal line of the occipital bone.

Splenius Capitis nerve

Posterior rami of spinal nerves.

Splenius Capitis function

Bilaterally extends the head and neck; unilaterally produces ipsilateral side bending and head rotation.

Splenius Cervicis origin

Nuchal ligament and spinous processes of C7-T3 or T4.

Splenius Cervicis insertion

Tubercles of the transverse processes of C1-C3 or C4.

Splenius Cervicis nerve

Posterior rami of spinal nerves.

Splenius Cervicis function

Bilaterally extends the head and neck; unilaterally produces ipsilateral side bending and head rotation.

Iliocostalis origin

Arises by a broad tendon from the posterior iliac crest, posterior sacrum, sacroiliac ligaments, and sacral/inferior lumbar spinous processes.

Iliocostalis insertion

Fibers run superiorly to the angles of the lower ribs and cervical transverse processes.

Iliocostalis nerve

Posterior rami of spinal nerves.

Iliocostalis function

Bilaterally extends the vertebral column and head; unilaterally produces lateral flexion and ipsilateral rotation.

Longissimus origin

Arises by a broad tendon from the posterior iliac crest, posterior sacrum, sacroiliac ligaments, and sacral/inferior lumbar spinous processes.

Longissimus insertion

Fibers run superiorly to the ribs (between tubercles and angles), transverse processes in thoracic/cervical regions, and the mastoid process.

Longissimus nerve

Posterior rami of spinal nerves.

Longissimus function

Bilaterally extends the vertebral column and head; unilaterally produces lateral flexion and ipsilateral rotation.

Spinalis origin

Arises by a broad tendon from the posterior iliac crest, posterior sacrum, sacroiliac ligaments, and sacral/inferior lumbar spinous processes.

Spinalis insertion

Fibers run superiorly to the spinous processes in the upper thoracic region and to the cranium.

Spinalis nerve

Posterior rami of spinal nerves.

Spinalis function

Bilaterally extends the vertebral column and head; unilaterally produces lateral flexion and ipsilateral rotation.

Semispinalis origin

Transverse processes of T12 - C4.

Semispinalis insertion

Fibers run superomedially to the occipital bone and spinous processes in the thoracic and cervical regions.

Semispinalis nerve

Posterior rami of spinal nerves.

Semispinalis function

Extends the head and thoracic/cervical regions; produces contralateral rotation.

Multifidus origin

Posterior sacrum, PSIS, sacroiliac ligaments, mammillary processes of lumbar vertebrae, and transverse processes of T1-3.

Multifidus insertion

Fibers pass superomedially to the entire length of the spinous processes, 2-4 segments superior to the origin.

Multifidus nerve

Posterior rami of spinal nerves.

Multifidus function

Stabilizes vertebrae during local movements and assists in contralateral rotation.

Rotatores origin

Transverse processes of vertebrae, most developed in the thoracic region.

Rotatores insertion

Junction of the lamina and transverse process (or spinous process) 1 or 2 segments superior to origin.

Rotatores nerve

Posterior rami of spinal nerves.

Rotatores function

Stabilize vertebrae and assist with local extension and contralateral rotation.

Interspinales origin

Superior surfaces of the spinous processes of cervical and lumbar vertebrae.

Interspinales insertion

Inferior surface of the spinous process of the vertebra superior to origin.

Interspinales nerve

Posterior rami of spinal nerves.

Interspinales function

Aid in extension and rotation of the vertebral column.

Intertransversari origin

Transverse processes of cervical and lumbar vertebrae.

Intertransversari insertion

Transverse process of the adjacent vertebra.

Intertransversari nerve

Posterior and anterior rami of spinal nerves.

Intertransversari function

Aid in lateral flexion and stabilize the vertebral column.

Levatores Costarum origin

Tips of the transverse processes of C7 and T1-T11.

Levatores Costarum insertion

Rib between the tubercle and the angle.

Levatores Costarum nerve

Posterior rami of C8-T11 spinal nerves.

Levatores Costarum function

Elevate ribs to assist respiration and assist with lateral flexion.

Rectus Capitis Posterior Major origin

Spinous process of C2.

Rectus Capitis Posterior Major insertion

Lateral portion of the inferior nuchal line.

Rectus Capitis Posterior Major nerve

Posterior rami of C1 (Suboccipital Nerve).

Rectus Capitis Posterior Major function

Extension of the head and ipsilateral rotation.

Rectus Capitis Posterior Minor origin

Posterior tubercle of the posterior arch of C1.

Rectus Capitis Posterior Minor insertion

Medial part of the inferior nuchal line.

Rectus Capitis Posterior Minor nerve

Posterior rami of C1.

Rectus Capitis Posterior Minor function

Extension of the head and ipsilateral rotation.

Obliquus Capitis Superior origin

Transverse process of C1.

Obliquus Capitis Superior insertion

Between the superior and inferior nuchal lines.

Obliquus Capitis Superior nerve

Posterior rami of C1.

Obliquus Capitis Superior function

Extension of the head and ipsilateral rotation.

Obliquus Capitis Inferior origin

Spinous process (posterior tubercle) of C2.

Obliquus Capitis Inferior insertion

Transverse process of C1.

Obliquus Capitis Inferior nerve

Posterior rami of C1.

Obliquus Capitis Inferior function

Ipsilateral rotation of the head.

Rectus Capitis Lateralis origin

Jugular process of the occipital bone.

Rectus Capitis Lateralis insertion

Transverse process of C1.

Rectus Capitis Lateralis function

Flexes the head and helps stabilize it.

Rectus Capitis Anterior origin

Base of the cranium anterior to the occipital bone.

Rectus Capitis Anterior insertion

Anterior surface of the lateral mass of C1.

Rectus Capitis Anterior function

Flexes the head.

Longus Capitis origin

Anterior tubercles of C3-C6 transverse processes.

Longus Capitis insertion

Basilar part of the occipital bone.

Longus Capitis function

Flexes the head.

Anterior Scalene origin

Transverse processes of C3-C6 vertebrae.

Anterior Scalene insertion

First rib.

Anterior Scalene function

Elevates the first rib, produces cervical flexion and ipsilateral side bending.

Middle Scalene origin

Posterior tubercles of the transverse processes of C2-C7.

Middle Scalene insertion

Upper surface of the first rib.

Middle Scalene function

Elevates the first rib and produces ipsilateral side bending.

Posterior Scalene origin

Posterior tubercles of the transverse processes of C5-C7.

Posterior Scalene insertion

External border of the second rib.

Posterior Scalene function

Elevates the second rib and produces ipsilateral side bending of the cervical spine.

Sternocleidomastoid origin

Sternal head (anterior manubrium) and Clavicular head (superior medial clavicle).

Sternocleidomastoid insertion

Lateral surface of the mastoid process and lateral half of the superior nuchal line.

Sternocleidomastoid nerve

Spinal Accessory Nerve (CN XI).

Sternocleidomastoid function

Bilaterally flexes the head forward or extends the neck; unilaterally produces ipsilateral side bending and contralateral rotation.

Trapezius origin

Superior nuchal line, EOP, nuchal ligament, and spinous processes of C7-T12.

Trapezius insertion

Lateral third of the clavicle, acromion, and spine of the scapula.

Trapezius nerve

Spinal Accessory Nerve (CN XI).

Trapezius function

Elevates, retracts, and rotates the scapula; produces cervical extension and ipsilateral side bending.

Latissimus Dorsi origin

Spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, and inferior 3 or 4 ribs.

Latissimus Dorsi insertion

Floor of the intertubercular sulcus (bicipital groove) of the humerus.

Latissimus Dorsi nerve

Thoracodorsal Nerve (C6, 7, 8).

Latissimus Dorsi function

Extends, adducts, and medially rotates the humerus.

Levator Scapulae origin

Posterior tubercles of the transverse processes of C1-C4.

Levator Scapulae insertion

Medial border of the scapula superior to the root of the spine.

Levator Scapulae nerve

Dorsal Scapular Nerve (C4, 5).

Levator Scapulae function

Elevates the scapula and tilts the glenoid cavity inferiorly.

Rhomboid Minor origin

Nuchal ligament and spinous processes of C7 and T1.

Rhomboid Minor insertion

Smooth triangular area at the medial end of the scapular spine.

Rhomboid Minor nerve

Dorsal Scapular Nerve (C4, 5).

Rhomboid Minor function

Retracts and rotates the scapula to depress the glenoid cavity; fixes the scapula to the thoracic wall.

Rhomboid Major origin

Spinous processes of T2-T5.

Rhomboid Major insertion

Medial scapular border below the scapular spine.